Method of expanding pressure welded passageway panels to precise thickness



Cd. 28, 1958 s. G. LUTHER, JR 2,857,658

METHOD OF EXPANDING PRESSURE WELDED PASSAGEWAY PANELS TO PRECISE THICKNESS Filed Dec. 9, 1955 IN VEN TOR. STEPHAN G. LUTHER JR.

United States Patent METHOD OF EXPANDING PRESSURE WELDED IEEZSSAGEWAY PANELS TO PRECISE THICK- Stephen G. Luther, Jr., Louisville, Ky., assignor to Reynolds Metals Company, Louisville, Ky., a corporation of Delaware Application December 9, 1955, Serial No. 552,195

3 Claims. (Cl. 29157.3)

This invention relates to roll bonded expanded passageway panels of precise expanded thickness.

The Long Patent #2,662,273 proposes to make expanded panels by roll bonding two foreshortened metal sheets, with a foreshortened stop-weld pattern of appropriate evaporator-circuit design interposed between them, to form a relatively elongate unexpanded panel and then hydraulically expanding its unbonded portions outwardly into contact with rigid flat-faced dies, which are spaced apart a distance precisely equal to the final overall thickness desired in the expanded panel.

In practicing this method, it has heretofore been difficult, if not impossible, to limit the outward expansion to the precise degree desired using rigid dies of reasonable size. For example, when the dies are spaced, say, 0.400 inch apart, the expanded thickness of the panel will vary upwardly from this figure due to the yield or give of the die platens and the associated die apparatus under the tremendous expansion pressures involved, which, for aluminum, normally approximate 3,000 p. s. i. more or less. The increase, in most cases, ranges from .005" to .020".

The principal object of the present invention is to provide a novel method of securing precision in the final thickness of the expanded panel.

Another object is to provide a novel method which enables a final thickness of precise dimension to be quickly and inexpensively achieved.

My invention resides in expanding a roll bonded passageway panel to a thickness greater than that desired and then flattening the panel to the precise thickness desired. This may be readily accomplished by expanding the panel outwardly against relatively movable dies or platens to a thickness slightly greater than the precise thickness desired, releasing the expansion pressure and then compressing the panel between platens to the precise thickness sought.

The invention is illustrated in the accompanying drawing wherein:

Figure 1 shows a panel which is expanded to the degree at which it first engages both dies;

Figure 2 shows the same panel in an over-expanded condition, the degree of the over-expansion being exaggerated for the sake of clearness; and

Figure 3 shows the panel when flattened to the precise final thickness desired.

In carrying out the invention, two foreshortened metal sheets, with a foreshortened stop-weld pattern of appropriate design interposed between them, are roll bonded to form a relatively elongate unexpanded panel. This panel 1 is placed between relatively movable dies or platens 2 and 3 and the movable die 3 is thereupon lowered until it engages the spacing block 4 which, in reality, is a gauge block having the precise thickness desired in the final panel. The panel is now connected to the expansion fluid system and its passageways 5 expanded usually with a liquid under expansion pressures normally ranging for aluminum from 1000 to 3500 p. s. i. but which may range from 200 to 10,000 p. s. i. depending upon such factors as the kind of metal, its gauge, composition, etc.

During the initial phase of the expansion, the Walls of the passageways 5 will bulge outwardly ultimately coming into initial contact with the dies 2 and 3. This stage of the expansion is shown in Figure 1. In accordance with my invention, the expansion operation continues until the walls of the passageways 5 are not only flattened as indicated at 6 in Figure 2 but the expanslon pressure is sufficient to raise the movable die 3 upwardly away from the gauge blocks 4. The extent to which this movement occurs preferably will be slight. However, it can and should be readily controlled and predetermined.

When the desired predetermined movement of the upper die 3 has been completed, the expansion fluid pressure preferably is released. The die 3 is now moved downwardly until it engages and rests upon the gauge blocks 4. This downward movement may be occasioned by gravity or by the application of an outside force. During the ensuing movement, the passageways are compressed until the overall thickness of the expanded panel is precisely identical to that of gauge blocks 4.

In practicing this invention, any suitable expansion pressures may be employed. Furthermore, this invention is applicable to roll bonded passageway panels which are expanded on one side only, which is to say that, in a roll bonded panel composed of two pressure welded sheets of metal, one sheet may be expanded along the unbonded stop-weld portions while the other sheet remains flat and unexpanded.

Having described my invention, I claim:

1. A method of expanding a pressure welded passageway panel composed of a pair of metal sheets containing unbonded potential passageway portions, comprising: expanding by fluid pressure unbonded portions outwardly between opposed platens to a panel thickness in excess of a predetermined panel thickness and, during such expansion, flattening the outermost surface portions of the expanded unbonded portions against the platens; releasing the fluid pressure; and compressing the expanded unbonded portions of said panel between opposing platens to reduce the panel thickness to said predetermined panel thickness.

2. The method of claim 1 wherein: said expansion and compression steps are performed between the same platens.

3. The method of claim 2 wherein: said compression step' is performed by moving the platens relatively inward toward each other.

References Cited in the file of this patent UNITED STATES PATENTS 

